Shell Recommendation/ Pressures Exceptable

[Live A Life Of Purpose]

Does anyone know if there is information out from companies on pressure testing from their loads they produce? I'm trying to purchase some shells for my 12 gauge with Low-Pressure loads. RST and Polywad are great shells, but sometimes the website is out of Bismuth for areas that I hunt and I was curious if anybody found information on this. I found some Bismuth produced by Kent that was 1 1/4 load at 1250 feet per second but you don't know the pressure produced would be acceptable for my Parker. I used to reload trap loads years ago, but I have been out of the mix on reloading for 15 years so I would love any direction if someone can share their experience. I know the feet per second and drams don't mean much without the pressure produced.